It is advantageous that the bolt of a semiautomatic firearm, such as a rifle, be held out of battery in an open position after the last cartridge has been expended. The bolt, held out of battery, immediately alerts the shooter that the magazine is empty and that it is time to reload. However, for some very popular rifles which use a rotary magazine, the bolt is not held open after the last round is fired, but is permitted to run back to battery under the biasing force of its recoil spring. Furthermore, semiautomatic firearm actions cycle so rapidly that it is not usually possible to observe the ammunition status as the rife is being fired. There is clearly an opportunity to improve the operation of such rifles by providing a rotary magazine which works in conjunction with a bolt catch